obliviousoblivious

Oblivious comes from Latin oblīviōsus ‘forgetful, oblivious’, and perhaps goes back to lēvis ‘smooth’.

1. Latinc. 75 BCE–200 CElēvis¹‘smooth’uncertain
2. Latinc. 75 BCE–200 CEoblīvīscor²‘to forget’plus root of lēvis
3. Latinc. 75 BCE–200 CEoblīvium²‘forgetfulness, oblivion’
4. Latinc. 75 BCE–200 CEoblīviōsus²‘forgetful, oblivious’
5. Middle Englishc. 1150–1500oblivious²‘forgetful’
6. Englishtodayoblivious²

1. ¹ Wiktionary, Latin obliviscor
2. ² Wiktionary, English oblivious

Earlier history uncertain. See Wiktionary.